In the application of graph theory to problems arising in network design, the requirements of the network can be expressed in terms of restrictions on the values of certain graph parameters such as connectivity, edge-connectivity, diameter, and independence number. In this paper, we focus on networks whose requirements translate into adjacency restrictions on the graph representing the network. More specifically, a graph G is said to have property P(m,n,k) if for any set of m + n distinct vertices there are at least k other vertices, each of which is adjacent to the first m vertices but not adjacent to any of the latter n vertices. The problem that arises is that of characterizing graphs having property P(m,n,k). In this paper, we present properties of graphs satisfying the adjacency property. In particular, for 9 = l(mod 4), a prime power, the Paley graph G, of order 9 is the graph whose vertices are elements of the finite field I F, ; two vertices are adjacent if and only if their difference is a quadratic residue. For any m, n , and k , we show that all sufficiently large Paley graphs satisfy P(m,n,k). 0 7993 by John Wiley & Sons, Inc.
Let m and n be nonnegative integers and it be a positive integer. A graph G is said to have property P(m, n, k) if for any set of m + n distinct vertices of G there are at least k other vertices, each of which is adjacent to the first m vertices of the set but not adjacent to any of the latter n vertices. The problem that arises is that of characterising graphs having property P(m, n, k). This problem has been considered by several authors and a number of results have been obtained. In this paper, we establish a lower bound on the order of a graph having property P(m, n, A:). Further, we show that all sufficiently large Paley graphs satisfy properties P(l, n, k) and P{n, 1, Jb).
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